Density is described as a substance's mass
per unit volume. Everything has a different density, and that
density affects other properties of the substance. For instance, a
liquid's density will determine how well objects are able float or
sink in it. This lab will look at the differences in the density of
salt-water and freshwater, and the effects that has on an object's
ability to float in each. The difference in the densities should
show us why things float better in seawater, as opposed to their
sinking in freshwater. The fact that seawater has salt dissolved in
it makes things more able to float in it. The salt in seawater
causes it to weigh more per unit volume than freshwater. The higher
weight causes saltwater to have a higher density, as density is
directly related to the mass of the substance. Also, different
amounts of salt will have different affects on the density. That is
why we will use a variety of amounts of salt in this lab, to see the
gradual changes in an egg's floating ability as it corresponds to the
density of the water it is in.

Methodology:

METHODOLOGY:

1. Put 400mL of water into each of the two
glasses.

2. Add five heaping teaspoons of salt to one
of the glasses. Mix until the salt is dissolved.

3. Carefully put one egg in each glass, and
observe what happens to each egg.

4. Now, take the eggs out of each glass, and
weigh them. Compare your results with the observation you made
before.

5. Now fill the other four glasses with
400mL water. Add one heaping teaspoon of salt to the first glass,
two to the second, three to the third, and four to the fourth. Mix
each glass thoroughly.

6. Now line up all six glasses that you
have, in order from the one with the most amount of salt added, down
to the glass with no salt.

7. Place an egg in each of the glasses, and
observe the position of each egg in its glass.

8. Using your observations, guess which
glass of water has the greatest density. Now, remove the eggs and
weigh each glass of water.

9. You can now calculate the density of the
water in each glass by using the equation density = mass/volume. Use
the weight that you just measured for the mass, and the volume of
water that you put in each glass, which was 400mL.

10. Compare the results of your calculations
to your guess. Were you correct about which glass had the highest
density?

Misc. Helpful Information/ Hints/
Suggestions:

To make the lab more fun for younger age
groups, allow them to use food coloring in the water, and to decorate
their "swimming" eggs.